1. Field of the Invention
The present invention pertains to a muffler assembly for a compressor, and, in particular, to a muffler assembly disposed at the inlet of a compressor in an oxygen concentration system that decreases the noise level of the system to produce a more tranquil operating environment.
2. Description of the Related Art
Compressors are utilized for compressing air or other gas at a low pressure, such as atmospheric pressure, to a higher pressure for subsequent use. One such application is the use of a compressor with an oxygen concentrator, where air is drawn into the compressor from the surrounding environment through an inlet port of the compressor and then compressed and passed through an outlet of the compressor to a molecular sieve bed of the oxygen concentrator where oxygen is separated from the other constituents of air for use by a patient.
A typical compressor includes a housing that houses a connecting rod assembly and a piston assembly which compress the air. The piston assembly generally consists of a compressor head connected to a valve plate, a piston sleeve connected to the valve plate, and a piston within the piston sleeve that moves within the piston sleeve in an up and down cycle. Compressing the gas generates noise from a variety of sources. For instance, running the connecting rod assembly and sucking gas into the compressor during the downstroke of the piston generates noise through the compressor intake port. Many pistons utilize a reed valve in the valve plate for directing the gas flow in and out of the compressor. Air flowing through such a reed valve generates a sound that is continually repeated as a result of the reciprocating motion of the piston. Furthermore, compressing gas during the upstroke of the piston generates a noise that travels back through the compressor intake port, while the turbulent flow of the gas as it travels at high velocity into an output cylinder also generates acoustic noise in a pulse setting fashion. Accordingly, in a conventional compressor assembly, a muffler is generally connected somewhere in the compressor system for muffling the noise of the compressor.
Several attempts have been made to develop a muffler for compressors. For example, some efforts have included placing foam filters within enclosed chambers with the gas entering the compressor being drawing through the filters. While such mufflers generally filter very high frequencies of noise, they have little affect on lower frequency sounds. Furthermore, these assemblies require numerous parts and typically occupy a large amount of space, which adversely impact the desirability of the muffler.
Other attempts to reduce compressor noise have utilized non-dissipative mufflers for reducing sound within a specific frequency range. Such mufflers utilize a resonator that is tuned to maximize the amount of attenuation by adjusting the length and diameter of the outlet with respect to the sides of the cylinder chamber. While these types of resonators are effective, they generally require extensive design work on the particular compressor size and then only work on soundwaves of a particular frequency.
U.S. Pat. No. 5,996,731 (“the '731 patent”) discloses a compressor muffler that utilizes a baffle and an attenuating element, both of which are provided in an intake conduit that is attached to the inlet of the compressor. The attenuating element is elongated and fits within an opening provided in the baffle. While this configuration is effective, it requires assembling the attenuating element within the intake conduit such that it is properly aligned in the opening of the baffle, which is a relatively cumbersome process. This configuration also does not minimize the space required for the muffler.
U.S. Pat. No. 6,382,931 (“the '931 patent”) is similar to the '731 patent except that it eliminates the attenuating element and teaches providing various configurations for the opening or openings in the baffle. The '931 patent also teaches providing multiple baffles with offset opening to define a tortuous path in the intake conduit. As with the, '731 patent, this configuration requires a specially configured intake conduit and does not minimize the space required for the muffler.
While many of these mufflers are believed to reduce the compressor noise, they are generally either difficult to design, only effectively reduce the sound associated with a particular wave frequency, require many components which result in an increase cost of the muffler in both materials and assembly labor.